1 /***************************************************************************
2 * Copyright (c) 2024 Microsoft Corporation
3 *
4 * This program and the accompanying materials are made available under the
5 * terms of the MIT License which is available at
6 * https://opensource.org/licenses/MIT.
7 *
8 * SPDX-License-Identifier: MIT
9 **************************************************************************/
10
11
12 /**************************************************************************/
13 /**************************************************************************/
14 /** */
15 /** GUIX Component */
16 /** */
17 /** Display Management (Display) */
18 /** */
19 /**************************************************************************/
20 #define GX_SOURCE_CODE
21
22
23 #include "gx_api.h"
24 #include "gx_display.h"
25
26 #define ALPHAVAL(_c) (GX_UBYTE)((_c) >> 24)
27 #define REDVAL(_c) (GX_UBYTE)((_c) >> 16)
28 #define GREENVAL(_c) (GX_UBYTE)((_c) >> 8)
29 #define BLUEVAL(_c) (GX_UBYTE)(_c)
30
31 #define ASSEMBLECOLOR(_a, _r, _g, _b) \
32 (((_a) << 24) | \
33 ((_r) << 16) | \
34 ((_g) << 8) | \
35 (_b))
36
37
38 /**************************************************************************/
39 /* */
40 /* FUNCTION RELEASE */
41 /* */
42 /* _gx_display_driver_32argb_pixel_blend PORTABLE C */
43 /* 6.1.3 */
44 /* AUTHOR */
45 /* */
46 /* Kenneth Maxwell, Microsoft Corporation */
47 /* */
48 /* DESCRIPTION */
49 /* */
50 /* Pixel blend function for 32argb color format. */
51 /* */
52 /* INPUT */
53 /* */
54 /* context Drawing context */
55 /* x X coordinate */
56 /* y Y coordinate */
57 /* color Color of line to write */
58 /* alpha blending value 0 to 255 */
59 /* */
60 /* OUTPUT */
61 /* */
62 /* None */
63 /* */
64 /* CALLS */
65 /* */
66 /* None */
67 /* */
68 /* CALLED BY */
69 /* */
70 /* GUIX Internal Code */
71 /* */
72 /* RELEASE HISTORY */
73 /* */
74 /* DATE NAME DESCRIPTION */
75 /* */
76 /* 05-19-2020 Kenneth Maxwell Initial Version 6.0 */
77 /* 09-30-2020 Kenneth Maxwell Modified comment(s), */
78 /* resulting in version 6.1 */
79 /* 12-31-2020 Kenneth Maxwell Modified comment(s), */
80 /* fix pixel blend logic, */
81 /* resulting in version 6.1.3 */
82 /* */
83 /**************************************************************************/
_gx_display_driver_32argb_pixel_blend(GX_DRAW_CONTEXT * context,INT x,INT y,GX_COLOR fcolor,GX_UBYTE alpha)84 VOID _gx_display_driver_32argb_pixel_blend(GX_DRAW_CONTEXT *context, INT x, INT y, GX_COLOR fcolor, GX_UBYTE alpha)
85 {
86
87 GX_UBYTE falpha, fred, fgreen, fblue;
88 GX_UBYTE balpha, bred, bgreen, bblue;
89 GX_UBYTE oalpha;
90 ULONG bcolor;
91 ULONG *put;
92 INT combined_alpha;
93
94
95 falpha = ALPHAVAL(fcolor);
96 falpha = (GX_UBYTE)((falpha * alpha) / 255);
97
98 /* Is the pixel non-transparent? */
99 if (falpha > 0)
100 {
101 /* calculate address of pixel */
102 put = (ULONG *)context -> gx_draw_context_memory;
103 put += context -> gx_draw_context_pitch * y;
104 put += x;
105
106 /* No need to blend if alpha value is 255. */
107 if (falpha == 255)
108 {
109 *put = (ULONG)fcolor;
110 return;
111 }
112
113 /* split foreground into alpha, red, green, and blue components */
114
115 fred = REDVAL(fcolor);
116 fgreen = GREENVAL(fcolor);
117 fblue = BLUEVAL(fcolor);
118
119 /* read background color */
120 bcolor = *put;
121
122 /* split background color into red, green, and blue components */
123 balpha = ALPHAVAL(bcolor);
124 bred = REDVAL(bcolor);
125 bgreen = GREENVAL(bcolor);
126 bblue = BLUEVAL(bcolor);
127
128 /* background alpha is inverse of foreground alpha */
129 combined_alpha = (falpha * balpha) / 0xff;
130
131 /* blend foreground and background, each color channel */
132 oalpha = (GX_UBYTE)(falpha + balpha - combined_alpha);
133 fred = (GX_UBYTE)((fred * falpha + bred * balpha - bred * combined_alpha) / oalpha);
134 fgreen = (GX_UBYTE)((fgreen * falpha + bgreen * balpha - bgreen * combined_alpha) / oalpha);
135 fblue = (GX_UBYTE)((fblue * falpha + bblue * balpha - bblue * combined_alpha) / oalpha);
136
137 /* re-assemble into 16-bit color and write it out */
138 *put = (ULONG)ASSEMBLECOLOR(oalpha, fred, fgreen, fblue);
139 }
140 }
141
142
